The present invention relates generally to improvements in a leveling pole and more particularly to an improved type measuring rod or surveying pole formed with a plurality of liner members telescopically slidable within each other and having an elliptic cross section.
Most of the conventional leveling poles in general use for determining a distance or measuring the height of trees are formed to make either a true circular cross sectional shape or a square cross sectional shape.
Referring to the aforesaid circular cross sectional leveling poles, however, they are so constructed that the inner liner members thereof are concentrically smaller in diameter than an outer liner member to form a smaller outer peripheral surface area one by one. Thus graduations must be marked in each different position on the peripheral surface area of the liner members so as to enable a user to read all the marked graduations with equal facility. This results in the marking of graduations being positionally restricted to a considerable extent and that, when viewed at a distance, all the marked graduations cannot always be confirmed with certainty, causing misreading more often than not. Further a particular mechanism is necessary to prevent each liner member from radially moving so as to always keep the marked graduations of liner members in an axially aligned position when the members are fully extended.
In the meanwhile, the aforesaid square cross sectional leveling poles are also disadventageous in that when a single one of the liner members gets deformed, as it happens very often, by dirt of external pressure or impact, all the liner members become difficult to telescopically slide with respect to each other, giving rise to a hindrance to the smooth operation and easy conveyance of the leveling pole.
Further according to the above-mentioned circular or square cross sectioned shape leveling poles, each liner member is provided in its one end with an interlockingly engageable stopper or locking button means for restrictively regulating the range wherein the members are slidable with respect to the other so that when extended one by one, they can always keep their respective determined length until at last all the liner members are fully extended to provide a determined full length of the leveling pole.
However, the prior stopper or locking means must be provided by forming an annular groove or a concave portion on the inner periphery of one end of an inner liner member and further forming a corresponding annular projection or convex portion on the outer periphery of one end of an outer liner member, thus bringing about disadvantages that they are technically very difficult to provide, and even if provided, too easily worn away to stand long use.
Further in case of extending the liner members provided with said locking button means, they cannot be positively engaged with each other without completely rushing the means into a hole engraved on an outer liner member.